S-locus structure of the Siberian NT1 selfing Arabidopsis lyrata population. (A) Phylogenetic tree of SCR proteins reveals clustering of NT1 SCR (green) and AhS12. (B) Comparison of the S-locus region of the A. lyrata NT1 genome assembly with the Arabidopsis halleri S12 haplotype (Durand et al. 2014). Links between S-loci are colored according to the Blast scores from highest (blue) to lowest (gray). SCR, SRK, and flanking U-box and ARK3 genes have green, orange, and purple borders, respectively. SRK gene appears to be completely absent from the S-locus of the NT1 A. lyrata selfing accession. The only Blast hit to SRK is a spurious hit to ARK3 as they both encode receptor-like serine/threonine kinases. (C) Protein sequence alignment of S-locus SCR genes from A. halleri and A. lyrata, including NT1. One of the eight conserved cysteines important for structural integrity has been lost from the NT1 SCR protein.